! Abstract: Intravascular (IV) catheters in the hospital setting are associated with a high rate of bacterial colonization, resulting in >20,000 deaths annually in the U.S. from catheter related blood stream infections (CR-BSIs). Newer commercial catheters pre-loaded with silver or antibiotics within their walls have failed to dramatically reduce this very significant problem. A variety of catheter lock solutions (catheters that are filled with these solutions when not in use) containing antibiotics, ethanol and other antimicrobials are currently employed in hospitals around the world. However none of the antimicrobial agents used in existing lock solutions are able to diffuse through the walls of the catheters and prevent infection and biofilm formation on the outer surfaces of the catheters. Further, microbial biofilm commonly formed on catheter surfaces is particularly resistant to antibiotic treatment owing to the inability of the antibiotics to penetrate the protective polysaccharide matrix associated with biofilm. Nitric oxide (NO) is an endogenous antimicrobial agent that kills planktonic bacteria as well as those microbes within a biofilm. Recent research has demonstrated that NO release from catheters surfaces using NO donors incorporated into the walls of the catheters is quite effective in preventing bacterial colonization. However, the use of exogenous NO donors within the walls of catheters will likely face significant FDA hurdles associated with ensuring the safety of the specific NO donors utilized. To move NO release catheters more quickly into clinical use, NOTA plans to create a simple NO release IV catheter lock solution that will be reconstituted from a dry powder state (in vial) by hospital personnel immediately before use, and then loaded into the IV catheter using a syringe. The solution will contain a proprietary mixture of S-nitrosogutathione (GSNO), a known carrier of NO within the human body, along with S-glutathione and/or ascorbate (vitamin C) as accelerants to control the rate of NO release from GSNO over many hours (in physiological saline solution). Phase I will focus on 1) optimizing the GSNO/additive formulation?s NO release kinetics and examining dry-state storage stability over 8 months of different recipes; 2) determining the duration and magnitude of NO release for different concentrations of lock solution reagents when loaded within the lumen of catheters made of different polymeric materials; and 3) assess the antimicrobial activity of different catheter tubing loaded with fresh GSNO/additive lock solutions (replaced daily) over 7 d periods against S. aureus and P. aeruginosa using a CDC bioreactor model. Given the known presence of GSNO in blood, the proposed use of antimicrobial GSNO-based catheter lock solutions should be a very safe, effective, and inexpensive new approach to greatly reduce the rates of CR-BSIs.